Medical, dental and other instruments are often made of high quality stainless steel that can be cleaned and sterilized between uses for different patients by high temperature steam under pressure. This sterilization procedure is quick, reliable, odorless, non-toxic and inexpensive. In contrast to this situation, more and more instruments are now made of heat-sensitive plastic, rubber, glass lenses and electronic components. These flexible, flexible-lensed, and rigid-lensed instruments allow relatively non-invasive diagnostic and treatment procedures within the body.
The non-invasive procedures allowed by these heat-sensitive instruments are responsible for great advances in medical practice. During use, these instruments can be contaminated with deadly pathogens such as the Human Immunodeficiency Virus (HIV), hepatitis viruses, and antibiotic drug-resistant tuberculosis and other bacteria. For these reasons, it is imperative that these heat-sensitive instruments be sterilized of all microbes prior to each use.
One of the problems associated with sterilizing medical instruments is that since many contain plastic and rubber materials, and/or contain lenses positioned with glue, or electrical or other materials, they cannot withstand sterilization by the heat of a steam sterilizer or dry heat oven. One method for sterilizing these devices includes low temperature ethylene oxide gas sterilization systems. However, these systems are very slow and require 24 or more hours of turn-around time.
Aqueous solutions of about 2.5% alkaline glutaraldehyde have been used to disinfect heat-sensitive medical devices since the 1960's. However, these glutaraldehyde solutions have many problems. First, while glutaraldehyde is far more antimicrobial especially against bacterial spores, at alkaline pH values than at acid pH values, in some compositions the glutaraldehyde becomes unstable when the pH value is increased from about 4.0 to about 8.5. Forty percent (40%) of the original glutaraldehyde concentration can be lost within two weeks at pH 8.5. To compensate for this loss of glutaraldehyde, the concentration of glutaraldehyde is originally set at twice the concentration needed for antimicrobial activity. Further, glutaraldehyde is a sensitizing, irritating, and toxic chemical. Thus, when the concentration of glutaraldehyde is doubled to compensate for instability, the toxicity is also increased.
Furthermore, the sporicidal activity of glutaraldehyde is relatively slow requiring an exposure time of ten (10) hours at 25.degree. C. Current compositions of glutaraldehyde may contain salts of acetic acid and glutaraldehyde concentrations of 3.5% to maximize sporicidal activity. This high concentration of glutaraldehyde in combination with the acrid fumes of acetic acid cause still further problems of chemical irritation and toxicity.
Slow tuberculocidal activity is another disadvantage of current glutaraldehyde compositions. They require 45 minutes of exposure at 25.degree. C. for 100% kill of populations of mycobacteria (TB). The increased temperature of 25.degree. C. as compared to 20.degree. C. has been used as an effort to increase the sporicidal and tuberculocidal properties of current glutaraldehyde compositions. Consequences of the increased temperature of 25.degree. C. is that users must provide heating devices, and the toxic glutaraldehyde fumes are further increased.
It can therefore be seen that there is a continuing need for an effective, practical, safe, affordable sterilant for heat-sensitive instruments, as well as for all applications that are beyond the scope of steam sterilization. This invention has as its primary objective the fulfillment of this need.
The inventor has now discovered that small concentrations (5% to 20%) of alcohol improve the tuberculocidal activity of glutaraldehyde. By improving the tuberculocidal activity of a glutaraldehyde composition, it is then possible to lower the concentration of glutaraldehyde and the recommended use temperature. The lower glutaraldehyde concentration and the lower use temperature decrease the toxicity of glutaraldehyde and eliminate the inconvenience of a heating device.
A buffer system can be selected that increases the pH value of the composition to about 7.2 without causing the loss of glutaraldehyde. The effect of selecting an alkaline buffer system that is compatible with glutaraldehyde is that the original or starting concentration of glutaraldehyde can be lowered. This in turn decreases the toxicity of the formula.
No acetate salts are added to the glutaraldehyde composition of the present invention, which decreases the acrid fumes and again lowers the overall toxicity of the formula.
It is therefore a primary objective of the present invention to provide an effective chemical disinfectant/sterilant for heat-sensitive medical, dental, and veterinary reusable devices which is stable at alkaline pH values without high concentrations of glutaraldehyde.
It is a further objective of the present invention to provide a chemical disinfectant/sterilant which is free of acetate salts.
It is still a further objective of the present invention to provide a chemical disinfectant/sterilant which does not require an outside source of heat to be tuberculocidal and/or sporicidal.
It is still a further objective of the present invention to provide a chemical disinfectant/sterilant which kills mycobacteria (TB) faster than currently available glutaraldehyde formulations.
It is yet a further objective of the present invention to provide a chemical disinfectant/sterilant which is economical to manufacture and safe to use.
These and other objectives will become apparent from the following description of the invention.